Welcome to the boards.
Thank youWelcome to the CBN!
Arrow logic from a hunters POV says shoot the shortest arrow that meets your xbow's stiffness, FOC needs and is accurate. The longer arrows get in the way especially with sharp broadheads on them and may add unnecessary weight.
From a practical POV, if you have 22" arrows that have the right nocks for your xbow and fly well and you are just target shooting, enjoy them.
About 2 inches...LOL
Seriously it just depends on how far you want your arrow to stick out past your bow.